we got a copter with a firmware modified by the seller. Unfortunatly we got no source files and the company seems not to be active any more. Is there a possibility to make a backup of the firmware?
Thanks a lot.
Its possible but has nothing to do with PX4. Please search for JTAG / SWD and read flash. You will need to solder a special connector and you need a JTAG adapter.
Generally the approach is hopeless though. The state of the art is moving very quickly and the reliability and robustness is improving as well. You might want to consider using the official Firmware instead (which would future-proof your operation).